Fluorometric High-Throughput Assay for Measuring Chlamydial Neutralizing Antibody

Chlamydia trachomatis is an obligate intracellular mucosotropic pathogen that causes human infections of global importance.C. trachomatis causes trachoma, the leading cause of preventable blindness worldwide, and is the most common cause of bacterial sexually transmitted disease. Although oculogenital infections are treatable with antibiotics, a vaccine is needed to controlC. trachomatis infection. Ideally, a vaccine would provide coverage against most, if not all, naturally occurring antigenically distinct serovariants. The development of a subunit vaccine to prevent oculogenital disease could be advanced by identifying chlamydial antigens that elicit pan-neutralizing antibodies, particularly among infected human populations of known risk factors. There is currently no objective high-throughputin vitro assay to screen human sera for neutralization to aid in identification of these antigens. This report describes an objective, high-throughputin vitro assay that measuresC. trachomatis -neutralizing antibodies. Antibody-mediated neutralization of chlamydial infection was performed in a 96-well microtiter format, and neutralization was quantified by immunostaining fixed cells followed by automated fluorometric analysis. This report shows that fluorometric analysis ofC. trachomatis infection directly correlates to labor-intensive manual inclusion counts. Furthermore, this report shows that fluorometry can be used to identifyC. trachomati s serovar- and serocomplex-specific neutralization. This objective, high-throughput analysis of serum neutralization is amenable to epidemiological studies of human chlamydial infection, human clinical vaccine trials, and preclinical animal model experiments ofChlamydia infection.